Boron-Containing Nucleating Agent for Polyphenylene Sulfide

ABSTRACT

A boron-containing nucleating agent is provided for use with a polyarylene sulfide. The boron-containing nucleating agent can have low crystallinity, a small particle size, and a large specific surface area. By selectively controlling certain aspects of the nucleating agent, the crystallization properties of a thermoplastic composition including the nucleating agent and a polyarylene sulfide can be significantly improved. For instance, the recrystallization temperature can be increased, which can allow the “cooling time” during a molding cycle to be substantially reduced. Through use of the boron-containing nucleating agent the recrystallization temperature can be greater than about 231° C.

RELATED APPLICATIONS

This application claims filing benefit of U.S. Provisional PatentApplication Ser. Nos. 61/576,505 filed on Dec. 16, 2011 and 61/665,384filed on Jun. 28, 2012, which are incorporated herein in their entirety.

BACKGROUND OF THE INVENTION

Polyarylene sulfide is a high performance polymer that can withstandhigh thermal, chemical, and mechanical stresses. Due to its relativelyslow crystallization rate, however, injection molding of parts frompolyarylene sulfide can be challenging. For example, to achieve thedesired degree of crystallization, molding is generally conducted at ahigh mold temperature (˜130° C. or more) and for a relatively long cycletime. Unfortunately, high mold temperatures typically dictate the needfor expensive and corrosive heating mediums (e.g., oil).

Attempts to address the problems noted above have generally involved theinclusion of nucleating agents in the polymer composition to helpimprove the crystallization properties. For instance, boron nitride hasoften been utilized as a nucleating agent. Boron nitride nucleatingagents exhibiting particular characteristics have been developed in anattempt to further improve characteristics of the polymers. For instancehexagonal boron nitride having a particular aspect ratio (e.g., greaterthan 2) and/or delaminated boron nitride particles with very high aspectratios and very small dimensions have been formed. High purity boronnitride particles that exhibit high crystallinity have also beenutilized as nucleating agents. In general, it has been assumed that thebest route to enhancing the desirable characteristics of the boronnitride is by decreasing the size and increasing the purity of theparticles.

To date, however, such attempts have not been fully satisfactory. Infact, the problems have become even more pronounced as variousindustries (e.g., electronic, automotive, etc.) are now demandinginjection molded parts with very small dimensional tolerances. In theseapplications, the polymer must have good flow properties so that it canquickly and uniformly fill the small spaces of the mold cavity. It hasbeen found, however, that conventional polyphenylene sulfides thatmanage to meet the requisite high flow requirement utilize nucleatingagents that tend to require a long cooling cycle, which can be a verycostly and time consuming step.

As such, a need exists for suitable nucleating agents for polyarylenesulfide that can provide a relatively short cycle time while stillachieving good mechanical properties.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a thermoplastic composition isdisclosed that includes a boron-containing nucleating agent and apolyarylene sulfide. The boron-containing nucleating agent can haverelatively poor crystallinity. For instance, the boron-containingnucleating agent can exhibit a graphitization index of greater thanabout 4. The boron-containing nucleating agent can also have a smallaverage particle size and a relatively large specific surface area, forinstance the ratio of the average particle size to the specific surfacearea can be between about 0.001 and about 1 (μm/m²/g). The thermoplasticcomposition can have a high recrystallization temperature, for examplegreater than about 231° C., which can translate into a faster speed ofrecrystallization and shorter cycle times for a product formationprocess.

Products as may be formed from the composition are also disclosed. Forexample, a centrifugal pump for circulating a coolant through anautomotive engine is disclosed. The pump comprises a pump impeller thatis configured to flow the coolant radially outward into a volutechamber; and a housing that encloses the pump impeller and volutechamber, wherein at least a portion of the pump impeller, the housing,or both comprise a molded part formed from the thermoplastic compositionthat comprises a polyarylene sulfide and boron-containing nucleatingagent.

Also disclosed are methods for molding the thermoplastic composition.The method comprises shaping a thermoplastic composition that comprisesa polyarylene sulfide and a boron-containing nucleating agent asdescribed herein. The method also includes cooling the thermoplasticcomposition. For instance, the method can include injection molding thepolyarylene sulfide composition.

Other features and aspects of the subject matter are set forth ingreater detail below.

BRIEF DESCRIPTION OF THE FIGURES

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a cross-sectional view of one embodiment of an injection moldapparatus that may be employed in the present invention; and

FIG. 2 illustrates a water pump that may be formed in accordance withone embodiment of the present invention.

FIG. 3 is a perspective view of an electronic device that can be formedin accordance with one embodiment of the present invention; and

FIG. 4 is a perspective view of the electronic device of FIG. 2, shownin closed configuration.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentinvention.

Generally speaking, the present disclosure is directed to aboron-containing nucleating agent that can be utilized for fastrecrystallization of a polyarylene sulfide. By selectively controllingcertain aspects of the nucleating agent, the crystallization propertiesof a thermoplastic composition including the nucleating agent and apolyarylene sulfide can be significantly improved. Among other things,the nucleating agent allows the “cooling time” during a molding cycle tobe substantially reduced. The decrease in cooling time can be evidencedby increase in the recrystallization temperature, which can be increasedby use of the boron-containing nucleating agent. Through use of theboron-containing nucleating agent, for example, the recrystallizationtemperature of a thermoplastic composition can be greater than about231° C., greater than about 232° C., or greater than about 233° C.

In addition to increasing the recrystallization temperature of athermoplastic composition, the boron-containing nucleating agent canincrease the recrystallization energy, which can also reduce coolingtime during a molding cycle. For example, a thermoplastic compositionincluding a polyarylene sulfide and the boron-containing nucleatingagent can exhibit recrystallization energy of greater than about 24kilojoules per gram (kJ/g), greater than about 24.5 kJ/g, or greaterthan about 25 kJ/g.

Addition of the boron-containing nucleating agent to the thermoplasticcomposition can lead to little or no change in other characteristics ofthe composition. For example, the melt viscosity of the composition canexhibit little or no change due to the presence of the nucleating agent.Thus, the utilization of the boron-containing nucleating agent cansignificantly improve the temperature and timing of the molding processwithout detrimental impact with regard to other process parameters.

Use of the boron-containing nucleating agent can also allow parts to bemolded at lower temperatures. For example, when considering an injectionmolding process, the mold temperature (e.g., temperature of a surface ofthe mold) may be from about 50° C. to about 120° C., in some embodimentsfrom about 60° C. to about 110° C., and in some embodiments, from about70° C. to about 90° C. In addition to minimizing the energy inputrequirements for the molding operation, such low mold temperatures maybe accomplished using cooling mediums that are less corrosive andexpensive than some conventional techniques. For example, liquid watermay be employed as a cooling medium. Further, the use of low moldtemperatures can also decrease the production of “flash” normallyassociated with high temperature molding operations. For example, thelength of any flash (also known as burrs) created during an injectionmolding operation may be about 0.17 millimeters or less, in someembodiments about 0.14 millimeters or less, and in some embodiments,about 0.13 millimeters or less.

The total cooling time can be determined from the point when thecomposition is injected into the mold cavity to the point that itreaches an ejection temperature at which it can be safely ejected.Exemplary cooling times may range, for instance, from about 1 to about60 seconds, in some embodiments from about 5 to about 40 seconds, and insome embodiments, from about 10 to about 35 seconds.

The boron-containing nucleating agent can exhibit relatively poorcrystallinity. For instance, the nucleating agent can exhibit asurprisingly high graphitization index such as greater than about 4,greater than about 5, or greater than about 6. In one embodiment, thegraphitization index can be between about 6 and about 10, for instancebetween about 7 and about 9.

Graphitization index (also commonly termed graphite index) is aparameter that describes the structural quality of the boron-containingparticles. Boron-containing particles such as boron nitride exist inseveral crystalline forms including hexagonal, which is similar tographite in structure; cubic, which is analogous to diamond; andwurtzite, which is similar to lonsdaleite (also called hexagonaldiamond). Following formation, the boron-containing particles can havedifferent degrees of crystallization. To measure this degree ofcrystallization, the structural figure of merit termed graphitizationindex has been developed. The graphitization index is derived from x-raydiffraction and is the ratio of the area under [(100)+(101)] peaks tothe area under the (102) peak. The graphitization index describes thedegree of order in the stacking of the layers along the c-axis of thematerial. The graphitization index can vary greatly, for instance fromabout 1 for well-ordered, highly crystalline particles up to about 50for the so-called turbostratic particles, in which the layers showrandom rotations and translation about the normal.

Surprisingly, it has been found that through utilization of aboron-containing nucleating agent that exhibits relatively lowcrystallinity, the recrystallization characteristics of the polyarylenesulfide can be greatly improved. Specifically, the recrystallizationtemperature and recrystallization energy can be increased, which candecrease cycle times when forming a molded product. In addition to thebeneficial functional capacity of the boron-containing nucleating agentduring a molding process, the boron-containing nucleating agent can alsoenhance the crystallization properties of the composition.

In conjunction with the surprisingly low crystallinity, theboron-containing nucleating agent can also have a small particle size.For instance, the nucleating agent can have an average particle size ofless than about 10 μm, less than about 9 μm, or less than about 8 μm.For example, the average particle size can be from about 0.5 μm to about10 μm, or from about 1 μm to about 9 μm. Average particle size can bedetermined according to sedimentation techniques, laser diffractionmethods, or any other suitable technique. For example, particle sizedistribution can be determined according to a standard testing methodsuch as ASTM D4464 or ASTM B822.

The nucleating agent can also have a large specific surface area. Thespecific surface area can be, for example, greater than about 15 m²/g,greater than about 17 m²/g, or greater than about 19 m²/g. In oneembodiment, the specific surface area can be quite large, for instancegreater than about 30 m²/g. The specific surface area can be determinedaccording to standard methods such as by the physical gas adsorptionmethod (B.E.T. method) with nitrogen as the adsorption gas, as isgenerally known in the art and described by Brunauer, Emmet, and Teller(J. Amer. Chem. Soc., vol. 60, February, 1938, pp. 309-319).

The combination of small particle size and large specific surface areacan provide a boron-containing nucleating agent that has a ratio ofaverage particle size to specific surface area of between about 0.001and about 1, for instance between about 0.01 and about 0.8, or betweenabout 0.02 and about 0.25.

The nucleating agent particles can have any overall shape. For example,the nucleating agent can include high aspect ratio particles having aneedle-like or plate-like structure. The boron-containing nucleationagent can also be in the form of aggregated particles, in which theindividual high aspect ratio particles are aggregated together with noparticular orientation or in a highly ordered fashion, for instance viaweak chemical bonds such as Van der Waals forces. Non-aggregated largerparticles can also be utilized. For instance particles including a largenumber of stacked plate-like primary particles can be utilized as wellas particles in which the primary structure is not evident, such asgranulated or pulverized particles formed of larger sintered bodies.

Suitable boron-containing nucleating agents may include anyboron-containing material as is generally known in the art that may beprovided with the disclosed characteristics. By way of example,boron-containing nucleating agent materials can include, withoutlimitation, boron nitride, sodium tetraborate, potassium tetraborate,calcium tetraborate, etc., as well as mixtures thereof. Boron nitride(BN) has been found to be particularly beneficial. Boron nitride existsin a variety of different crystalline forms (e.g., h-BN—hexagonal,c-BN—cubic or spharlerite, and w-BN—wurtzite), any of which cangenerally be employed in the present invention. The hexagonalcrystalline form may be utilized in one embodiment due to its stabilityand softness.

The nucleating agent can be formed according to any standard formationmethod. By way of example, boron nitride particles may be formedaccording to a process that includes a high temperature sintering ofraw, essentially turbostratic powders as may be formed from reaction ofboric acid with boron trioxide. Sintering can generally be carried outat a temperature of between about 1400° C. to about 2300° C. for aperiod of between about 0.5 and about 12 hours. Sintering can take placein an inert atmosphere, such as argon, or optionally in a nitrogen richatmosphere. Sintering can be carried out under vacuum or in apressurized atmosphere, as is known. A large sintered body can begranulated or pulverized according to any suitable process to form thenucleating agent particles including, without limitation, jaw crushingor roll crushing. Beneficially, as the boron-containing nucleating agenthas a relatively poor crystallinity, the formation process can becarried out at a lower temperature as compared to higher crystallineparticles. This can lead to cost savings in a formation process as wellas for the products formed thereby.

Of course, other formation processes as are known in the art mayalternatively be utilized such as reaction of boric acid with melaminefollowed by calcination (e.g., at a temperature of from about 40° C. toabout 200° C. and a relative humidity of greater than about 5%) andaddition of a crystallization catalyst such as boric acid or a boratesalt of an alkali metal. By utilization of a small amount ofcrystallization catalyst, the graphitization index can be controlled toprovide a nucleation agent having the desired level of crystallinity.For example, the crystallization catalyst can be used in an amount suchthat the molar ratio of the nitrogen of the boron nitride to thecrystallization catalyst is greater than about 300 to obtain a boronnitride nucleation agent having a graphitization index of greater thanabout 4.

The nucleating agent component (i.e., one or more nucleating agents)typically constitutes from about 0.01 wt. % to about 6 wt. %, in someembodiments from about 0.05 wt. % to about 3 wt. %, and in someembodiments, from about 0.1 wt. % to about 2 wt. % of the thermoplasticcomposition.

A thermoplastic composition that includes the boron-containingnucleating agent can also include at least one polyarylene sulfide,which is generally able to withstand relatively high temperatureswithout melting. Although the actual amount may vary depending ondesired application, polyarylene sulfide(s) typically constitute fromabout 30 wt % to about 95 wt. %, in some embodiments from about 35 wt. %to about 90 wt. %, and in some embodiments, from about 40 wt. % to about80 wt. % of the thermoplastic composition. The polyarylene sulfide(s)generally have repeating units of the formula:

—[(Ar¹)_(n)—X]_(m)—[(Ar²)_(i)—Y]_(j)—[(Ar³)_(k)—Z]_(l)[(Ar⁴)_(o)—W]_(p)—

wherein,

Ar¹, Ar², Ar³, and Ar⁴ are independently arylene units of 6 to 18 carbonatoms;

W, X, Y, and Z are independently bivalent linking groups selected from—SO₂—, —S—, —SO—, —CO—, —O—, —C(O)O— or alkylene or alkylidene groups of1 to 6 carbon atoms, wherein at least one of the linking groups is —S—;and

n, m, i, j, k, l, o, and p are independently 0, 1, 2, 3, or 4, subjectto the proviso that their sum total is not less than 2.

The arylene units Ar¹, Ar², Ar³, and Ar⁴ may be selectively substitutedor unsubstituted. Advantageous arylene units are phenylene, biphenylene,naphthylene, anthracene and phenanthrene. The polyarylene sulfidetypically includes more than about 30 mol %, more than about 50 mol %,or more than about 70 mol % arylene sulfide (—S—) units. For example,the polyarylene sulfide may include at least 85 mol % sulfide linkagesattached directly to two aromatic rings. In one particular embodiment,the polyarylene sulfide is a polyphenylene sulfide, defined herein ascontaining the phenylene sulfide structure —(C₆H₄—S)_(n)— (wherein n isan integer of 1 or more) as a component thereof.

Synthesis techniques that may be used in making a polyarylene sulfideare generally known in the art. By way of example, a process forproducing a polyarylene sulfide can include reacting a material thatprovides a hydrosulfide ion (e.g., an alkali metal sulfide) with adihaloaromatic compound in an organic amide solvent. The alkali metalsulfide can be, for example, lithium sulfide, sodium sulfide, potassiumsulfide, rubidium sulfide, cesium sulfide or a mixture thereof. When thealkali metal sulfide is a hydrate or an aqueous mixture, the alkalimetal sulfide can be processed according to a dehydrating operation inadvance of the polymerization reaction. An alkali metal sulfide can alsobe generated in situ. In addition, a small amount of an alkali metalhydroxide can be included in the reaction to remove or react impurities(e.g., to change such impurities to harmless materials) such as analkali metal polysulfide or an alkali metal thiosulfate, which may bepresent in a very small amount with the alkali metal sulfide.

The dihaloaromatic compound can be, without limitation, ano-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene,dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoicacid, dihalodiphenyl ether, dihalodiphenyl sulfone, dihalodiphenylsulfoxide or dihalodiphenyl ketone. Dihaloaromatic compounds may be usedeither singly or in any combination thereof. Specific exemplarydihaloaromatic compounds can include, without limitation,p-dichlorobenzene; m-dichlorobenzene; o-dichlorobenzene;2,5-dichlorotoluene; 1,4-dibromobenzene; 1,4-dichloronaphthalene;1-methoxy-2,5-dichlorobenzene; 4,4′-dichlorobiphenyl;3,5-dichlorobenzoic acid; 4,4′-dichlorodiphenyl ether;4,4′-dichlorodiphenylsulfone; 4,4′-dichlorodiphenylsulfoxide; and4,4′-dichlorodiphenyl ketone. The halogen atom can be fluorine,chlorine, bromine or iodine, and two halogen atoms in the samedihalo-aromatic compound may be the same or different from each other.In one embodiment, o-dichlorobenzene, m-dichlorobenzene,p-dichlorobenzene or a mixture of two or more compounds thereof is usedas the dihalo-aromatic compound. As is known in the art, it is alsopossible to use a monohalo compound (not necessarily an aromaticcompound) in combination with the dihaloaromatic compound in order toform end groups of the polyarylene sulfide or to regulate thepolymerization reaction and/or the molecular weight of the polyarylenesulfide.

The polyarylene sulfide(s) may be homopolymers or copolymers. Forinstance, selective combination of dihaloaromatic compounds can resultin a polyarylene sulfide copolymer containing not less than twodifferent units. For instance, when p-dichlorobenzene is used incombination with m-dichlorobenzene or 4,4′-dichlorodiphenylsulfone, apolyarylene sulfide copolymer can be formed containing segments havingthe structure of formula:

and segments having the structure of formula:

or segments having the structure of formula:

In another embodiment, a polyarylene sulfide copolymer may be formedthat includes a first segment with a number-average molar mass Mn offrom 1000 to 20,000 g/mol. The first segment may include first unitsthat have been derived from structures of the formula:

where the radicals R¹ and R², independently of one another, are ahydrogen, fluorine, chlorine or bromine atom or a branched or unbranchedalkyl or alkoxy radical having from 1 to 6 carbon atoms; and/or secondunits that are derived from structures of the formula:

The first unit may be p-hydroxybenzoic acid or one of its derivatives,and the second unit may be composed of 2-hydroxynaphthalene-6-carboxylicacid. The second segment may be derived from a polyarylene sulfidestructure of the formula:

—[Ar—S]_(q)—

where Ar is an aromatic radical, or more than one condensed aromaticradical, and q is a number from 2 to 100, in particular from 5 to 20,The radical Ar may be a phenylene or naphthylene radical. in oneembodiment, the second segment may be derived frompoly(m-thiophenylene), from poly(o-thiophenylene), or frompoly(p-thiophenylene).

The polyarylene sulfide(s) may be linear, semi-linear, branched orcrosslinked. Linear polyarylene sulfides typically contain 80 mol % ormore of the repeating unit —(Ar—S)—. Such linear polymers may alsoinclude a small amount of a branching unit or a cross-linking unit, butthe amount of branching or cross-linking units is typically less thanabout 1 mol % of the total monomer units of the polyarylene sulfide. Alinear polyarylene sulfide polymer may be a random copolymer or a blockcopolymer containing the above-mentioned repeating unit. Semi-linearpolyarylene sulfides may likewise have a cross-linking structure or abranched structure introduced into the polymer a small amount of one ormore monomers having three or more reactive functional groups. By way ofexample, monomer components used in forming a semi-linear polyarylenesulfide can include an amount of polyhaloaromatic compounds having twoor more halogen substituents per molecule which can be utilized inpreparing branched polymers. Such monomers can be represented by theformula R′X_(n), where each X is selected from chlorine, bromine, andiodine, n is an integer of 3 to 6, and R′ is a polyvalent aromaticradical of valence n which can have up to about 4 methyl substituents,the total number of carbon atoms in R′ being within the range of 6 toabout 16. Examples of some polyhaloaromatic compounds having more thantwo halogens substituted per molecule that can be employed in forming asemi-linear polyarylene sulfide include 1,2,3-trichlorobenzene,1,2,4-trichlorobenzene, 1,3-dichloro-5-bromobenzene,1,2,4-triiodobenzene, 1,2,3,5-tetrabromobenzene, hexachlorobenzene,1,3,5-trichloro-2,4,6-trimethylbenzene, 2,2′,4,4′-tetrachlorobiphenyl,2,2′,5,5′-tetra-iodobiphenyl,2,2′,6,6′-tetrabromo-3,3′,5,6-tetramethylbiphenyl,1,2,3,4-tetrachloronaphthalene, 1,2,4-tribromo-6-methylnaphthalene,etc., and mixtures thereof.

Regardless of the particular structure, the number average molecularweight of the polyarylene sulfide is typically about 15,000 g/mol ormore, and in some embodiments, about 30,000 g/mol or more. In certaincases, a small amount of chlorine may be employed during formation ofthe polyarylene sulfide. Nevertheless, the polyarylene sulfide willstill have a low chlorine content, such as about 1000 ppm or less, insome embodiments about 900 ppm or less, in some embodiments from about 1to about 800 ppm, and in some embodiments, from about 2 to about 700ppm. In certain embodiments, however, the polyarylene sulfide isgenerally free of chlorine or other halogens.

In addition to the boron-containing nucleating agent and polyarylenesulfide, the thermoplastic composition may also contain a variety ofother different components to help improve its overall properties. Onesuitable additive that may be employed to improve the mechanicalproperties of the composition is an impact modifier. Examples ofsuitable impact modifiers may include, for instance, polyepoxides,polyurethanes, polybutadiene, acrylonitrile-butadiene-styrene,polysiloxanes etc., as well as mixtures thereof. In one particularembodiment, a polyepoxide modifier is employed that contains at leasttwo oxirane rings per molecule. The polyepoxide may be a linear orbranched, homopolymer or copolymer (e.g., random, graft, block, etc.)containing terminal epoxy groups, skeletal oxirane units, and/or pendentepoxy groups. The monomers employed to form such polyepoxides may vary.In one particular embodiment, for example, the polyepoxide modifiercontains at least one epoxy-functional (meth)acrylic monomericcomponent. The term “(meth)acrylic” includes acrylic and methacrylicmonomers, as well as salts or esters thereof, such as acrylate andmethacrylate monomers. Suitable epoxy-functional (meth)acrylic monomersmay include, but are not limited to, those containing 1,2-epoxy groups,such as glycidyl acrylate and glycidyl methacrylate. Other suitableepoxy-functional monomers include allyl glycidyl ether, glycidylethacrylate, and glycidyl itoconate.

If desired, additional monomers may also be employed in the polyepoxideto help achieve the desired melt viscosity. Such monomers may vary andinclude, for example, ester monomers, (meth)acrylic monomers, olefinmonomers, amide monomers, etc. In one particular embodiment, forexample, the polyepoxide modifier includes at least one linear orbranched α-olefin monomer, such as those having from 2 to 20 carbonatoms and preferably from 2 to 8 carbon atoms. Specific examples includeethylene, propylene, 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene;1-pentene; 1-pentene with one or more methyl, ethyl or propylsubstituents; 1-hexene with one or more methyl, ethyl or propylsubstituents; 1-heptene with one or more methyl, ethyl or propylsubstituents; 1-octene with one or more methyl, ethyl or propylsubstituents; 1-nonene with one or more methyl, ethyl or propylsubstituents; ethyl, methyl or dimethyl-substituted 1-decene;1-dodecene; and styrene. Particularly desired α-olefin comonomers areethylene and propylene. In one particularly desirable embodiment of thepresent invention, the polyepoxide modifier is a copolymer formed froman epoxy-functional (meth)acrylic monomeric component and α-olefinmonomeric component. For example, the polyepoxide modifier may bepoly(ethylene-co-glycidyl methacrylate). One specific example of asuitable polyepoxide modifier that may be used in the present inventionis commercially available from Arkema under the name Lotader® AX8840.Lotader® AX8950 has a melt flow rate of 5 g/10 min and has a glycidylmethacrylate monomer content of 8 wt. %.

Still another suitable additive that may be employed to improve themechanical properties of the thermoplastic composition is anorganosilane coupling agent. The coupling agent may, for example, be anyalkoxysilane coupling agent as is known in the art, such asvinlyalkoxysilanes, epoxyalkoxysilanes, aminoalkoxysilanes,mercaptoalkoxysilanes, and combinations thereof. Aminoalkoxysilanecompounds typically have the formula: R⁵—Si—(R⁶)₃, wherein R⁵ isselected from the group consisting of an amino group such as NH₂; anaminoalkyl of from about 1 to about 10 carbon atoms, or from about 2 toabout 5 carbon atoms, such as aminomethyl, aminoethyl, aminopropyl,aminobutyl, and so forth; an alkene of from about 2 to about 10 carbonatoms, or from about 2 to about 5 carbon atoms, such as ethylene,propylene, butylene, and so forth; and an alkyne of from about 2 toabout 10 carbon atoms, or from about 2 to about 5 carbon atoms, such asethyne, propyne, butyne and so forth; and wherein R⁶ is an alkoxy groupof from about 1 to about 10 atoms, or from about 2 to about 5 carbonatoms, such as methoxy, ethoxy, propoxy, and so forth. In oneembodiment, R⁵ is selected from the group consisting of aminomethyl,aminoethyl, aminopropyl, ethylene, ethyne, propylene and propyne, and R⁶is selected from the group consisting of methoxy groups, ethoxy groups,and propoxy groups. In another embodiment, R⁵ is selected from the groupconsisting of an alkene of from about 2 to about 10 carbon atoms such asethylene, propylene, butylene, and so forth, and an alkyne of from about2 to about 10 carbon atoms such as ethyne, propyne, butyne and so forth,and R⁶ is an alkoxy group of from about 1 to about 10 atoms, such asmethoxy group, ethoxy group, propoxy group, and so forth. A combinationof various aminosifanes may also be included in the mixture.

Some representative examples of aminosilane coupling agents that may beincluded in the mixture include aminopropyl triethoxysilane, aminoethyltriethoxysilane, aminopropyl trimethoxysilane, aminoethyltrimethoxysilane, ethylene trimethoxysilane, ethylene triethoxysilane,ethyne trimethoxysilane, ethyne triethoxysilane,aminoethylaminopropyltrimethoxysilane, 3-aminopropyl triethoxysilane,3-aminopropyl trimethoxysilane, 3-aminopropyl methyl dimethoxysilane or3-aminopropyl methyl diethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyl trimethoxysilane,N-phenyl-3-aminopropyl trimethoxysilane,bis(3-aminopropyl)tetramethoxysilane, bis(3-aminopropyl tetraethoxydisiloxane, and combinations thereof. The amino silane may also be anaminoalkoxysilane, such as γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane,γ-aminopropylmethyldiethoxysilane,N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,γ-diallylaminopropyltrimethoxysilane andγ-diallylaminopropyltrimethoxysilane. One suitable amino silane is3-aminopropyltriethoxysilane which is available from Degussa, SigmaChemical Company, and Aldrich Chemical Company.

Fillers may also be employed in the thermoplastic composition to helpachieve the desired properties and/or color. When employed, such mineralfillers typically constitute from about 5 wt. % to about 60 wt. %, insome embodiments from about 10 wt. % to about 50 wt. %, and in someembodiments, from about 15 wt. % to about 45 wt. % of the thermoplasticcomposition. Clay minerals may be particularly suitable for use in thepresent invention. Examples of such clay minerals include, for instance,talc (Mg₃Si₄O₁₀(OH)₂), halloysite (Al₂Si₂O₅(OH)₄), kaolinite(Al₂Si₂O₅(OH)₄), illite ((K,H₃O)(Al,Mg,Fe)₂ (Si,Al)₄O₁₀[(OH)₂,(H₂O)]),montmorillonite (Na, Ca)_(0.33)(Al,Mg)₂Si₄O₁₀(OH)₂.nH₂O), vermiculite((MgFe,Al)₃(Al,Si)₄O₁₀(OH)₂.4H₂O), palygorskite((Mg,Al)₂Si₄O₁₀(OH).4(H₂O)), pyrophyllite (Al₂Si₄O₁₀(OH)₂), etc., aswell as combinations thereof. In lieu of, or in addition to, clayminerals, still other mineral fillers may also be employed. For example,other suitable silicate fillers may also be employed, such as calciumsilicate, aluminum silicate, mica, diatomaceous earth, wollastonite, andso forth. Mica, for instance, may be a particularly suitable mineral foruse in the present invention. There are several chemically distinct micaspecies with considerable variance in geologic occurrence, but all haveessentially the same crystal structure. As used herein, the term “mica”is meant to generically include any of these species, such as muscovite(KAl₂(AlSi₃)O₁₀(OH)₂), biotite (K(Mg,Fe)₃(AlSi₃)O₁₀(OH)₂), phlogopite(KMg₃(AlSi₃)O₁₀(OH)₂), lepidolite (K(Li,Al)₂₋₃(AlSi₃)O₁₀(OH)₂),glauconite (K,Na)(Al,Mg,Fe)₂(Si,Al)₄O₁₀(OH)₂), etc., as well ascombinations thereof.

Fibrous fillers may also be employed in the thermoplastic composition.When employed, such fibrous fillers typically constitute from about 5wt. % to about 60 wt. %, in some embodiments from about 10 wt. % toabout 50 wt. %, and in some embodiments, from about 15 wt. % to about 45wt. % of the thermoplastic composition. The fibrous fillers may includeone or more fiber types including, without limitation, polymer fibers,glass fibers, carbon fibers, metal fibers, and so forth, or acombination of fiber types. In one embodiment, the fibers may be choppedglass fibers or glass fiber rovings (tows). Fiber diameters can varydepending upon the particular fiber used and are available in eitherchopped or continuous form. The fibers, for instance, can have adiameter of less than about 100 μm, such as less than about 50 μm. Forinstance, the fibers can be chopped or continuous fibers and can have afiber diameter of from about 5 μm to about 50 μm, such as from about 5μm to about 15 μm.

Lubricants may also be employed in the thermoplastic composition thatare capable of withstanding the processing conditions of poly(arylenesulfide) (typically from about 290° C. to about 320° C.) withoutsubstantial decomposition. Exemplary of such lubricants include fattyacids esters, the salts thereof, esters, fatty acid amides, organicphosphate esters, and hydrocarbon waxes of the type commonly used aslubricants in the processing of engineering plastic materials, includingmixtures thereof. Suitable fatty acids typically have a backbone carbonchain of from about 12 to about 60 carbon atoms, such as myristic acid,palmitic acid, stearic acid, arachic acid, montanic acid, octadecinicacid, parinric acid, and so forth. Suitable esters include fatty acidesters, fatty alcohol esters, wax esters, glycerol esters, glycol estersand complex esters. Fatty acid amides include fatty primary amides,fatty secondary amides, methylene and ethylene bisamides andalkanolamides such as, for example, palmitic acid amide, stearic acidamide, oleic acid amide, N,N′-ethylenebisstearamide and so forth. Alsosuitable are the metal salts of fatty acids such as calcium stearate,zinc stearate, magnesium stearate, and so forth; hydrocarbon waxes,including paraffin waxes, polyolefin and oxidized polyolefin waxes, andmicrocrystalline waxes. Particularly suitable lubricants are acids,salts, or amides of stearic acid, such as pentaerythritol tetrastearate,calcium stearate, or N,N′-ethylenebisstearamide. When employed, thelubricant(s) typically constitute from about 0.05 wt. % to about 1.5 wt.%, and in some embodiments, from about 0.1 wt. % to about 0.5 wt. % ofthe thermoplastic composition.

Still another additive that may be employed in the thermoplasticcomposition is a disulfide compound. Without wishing to be bound by anyparticular theory, the disulfide compound can undergo a polymer scissionreaction with a polyarylene sulfide during melt processing that evenfurther lowers the overall melt viscosity of the composition. Whenemployed, disulfide compounds typically constitute from about 0.01 wt. %to about 3 wt. %, in some embodiments from about 0.02 wt. % to about 1wt. %, and in some embodiments, from about 0.05 to about 0.5 wt. % ofthe composition. The ratio of the amount of the polyarylene sulfide tothe amount of the disulfide compound may likewise be from about 1000:1to about 10:1, from about 500:1 to about 20:1, or from about 400:1 toabout 30:1. Suitable disulfide compounds are typically those having thefollowing formula:

R³—S—S—R⁴

wherein R³ and R⁴ may be the same or different and are hydrocarbongroups that independently include from 1 to about 20 carbons. Forinstance, R³ and R⁴ may be an alkyl, cycloalkyl, aryl, or heterocyclicgroup. In certain embodiments, R³ and R⁴ are generally nonreactivefunctionalities, such as phenyl, naphthyl, ethyl, methyl, propyl, etc.Examples of such compounds include diphenyl disulfide, naphthyldisulfide, dimethyl disulfide, diethyl disulfide, and dipropyldisulfide. R³ and R⁴ may also include reactive functionality at terminalend(s) of the disulfide compound. For example, at least one of R³ and R⁴may include a terminal carboxyl group, hydroxyl group, a substituted ornon-substituted amino group, a nitro group, or the like. Examples ofcompounds may include, without limitation, 2,2′-diaminodiphenyldisulfide, 3,3′-diaminodiphenyl disulfide, 4,4′-diaminodiphenyldisulfide, dibenzyl disulfide, dithiosalicyclic acid, dithioglycolicacid, α,α′-dithiodilactic acid, β,β′-dithiodilactic acid,3,3′-dithiodipyridine, 4,4′-dithiomorpholine,2,2′-dithiobis(benzothiazole), 2,2′-dithiobis(benzimidazole),2,2′-dithiobis(benzoxazole) and 2-(4′-morpholinodithio)benzothiazole.

Still other additives that can be included in the composition mayinclude, for instance, antimicrobials, pigments, antioxidants,stabilizers, surfactants, waxes, flow promoters, solid solvents, andother materials added to enhance properties and processability.

The manner in which the boron-containing nucleating agent, polyarylenesulfide, and other optional additives are combined may vary as is knownin the art. For instance, the materials may be supplied eithersimultaneously or in sequence to a melt processing device thatdispersively blends the materials. Batch and/or continuous meltprocessing techniques may be employed. For example, a mixer/kneader,Banbury mixer, Farrel continuous mixer, single-screw extruder,twin-screw extruder, roll mill, etc., may be utilized to blend and meltprocess the materials. One particularly suitable melt processing deviceis a co-rotating, twin-screw extruder (e.g., Leistritz co-rotating fullyintermeshing twin screw extruder). Such extruders may include feedingand venting ports and provide high intensity distributive and dispersivemixing. For example, the polyarylene sulfide and nucleating agent may befed to the same or different feeding ports of a twin-screw extruder andmelt blended to form a substantially homogeneous melted mixture. Meltblending may occur under high shear/pressure and heat to ensuresufficient dispersion. For example, melt processing may occur at atemperature of from about 50° C. to about 500° C., and in someembodiments, from about 100° C. to about 250° C. Likewise, the apparentshear rate during melt processing may range from about 100 seconds⁻¹ toabout 10,000 seconds⁻¹, and in some embodiments, from about 500seconds⁻¹ to about 1,500 seconds⁻¹. Of course, other variables, such asthe residence time during melt processing, which is inverselyproportional to throughput rate, may also be controlled to achieve thedesired degree of homogeneity.

Besides melt blending, other techniques may also be employed to combinethe nucleating agent and the polyarylene sulfide. For example, thenucleating agent may be supplied during one or more stages of thepolymerization of the polyarylene sulfide, such as to the polymerizationapparatus. Although it may be introduced at any time, it is typicallydesired to apply the nucleating agent before polymerization has beeninitiated, and typically in conjunction with the precursor monomers forthe polyarylene sulfide. The reaction mixture is generally heated to anelevated temperature within the polymerization reactor vessel toinitiate melt polymerization of the reactants.

Regardless of the manner in which they are combined together, the degreeand rate of crystallization of the thermoplastic composition may besignificantly enhanced by the boron-containing nucleating agent. Forexample, the crystallization potential of the thermoplastic composition(prior to molding) may be about 52% or more, in some embodiments about55% or more, in some embodiments about 58% or more, and in someembodiments, from about 60% to about 95%. The crystallization potentialmay be determined by subtracting the latent heat of crystallization(ΔH_(c)) from the latent heat of fusion (ΔH_(f)), dividing thisdifference by the latent heat of fusion, and then multiplying by 100.The latent heat of fusion (ΔH_(f)) and latent heat of crystallization(ΔH_(c)) may be determined by Differential Scanning calorimetry (“DSC”)as is well known in the art and in accordance with ISO Standard 10350.The latent heat of crystallization may, for example, be about 15 Joulesper gram (“J/g”) or less, in some embodiments about 12 J/g or less, andin some embodiments, from about 1 to about 10 J/g. The latent heat offusion may likewise be about 15 Joules per gram (“J/g”) or more, in someembodiments about 18 J/g or more, and in some embodiments, from about 20to about 28 J/g.

In addition, the thermoplastic composition may also crystallize at alower temperature than would otherwise occur absent the presence of thenucleating agent. For example, the crystallization temperature (prior tomolding) of the thermoplastic composition may about 250° C. or less, insome embodiments from about 100° C. to about 245° C., and in someembodiments, from about 150° C. to about 240° C. The melting temperatureof the thermoplastic composition may also range from about 250° C. toabout 320° C., and in some embodiments, from about 265° C. to about 300°C. The melting and crystallization temperatures may be determined as iswell known in the art using differential scanning calorimetry inaccordance with ISO Test No. 11357. Even at such melting temperatures,the ratio of the deflection temperature under load (“DTUL”), a measureof short term heat resistance, to the melting temperature may stillremain relatively high. For example, the ratio may range from about 0.65to about 1.00, in some embodiments from about 0.70 to about 0.99, and insome embodiments, from about 0.80 to about 0.98. The specific DTULvalues may, for instance, range from about 230° C. to about 300° C., insome embodiments from about 240° C. to about 290° C., and in someembodiments, from about 250° C. to about 280° C. Such high DTUL valuescan, among other things, allow the use of high speed processes oftenemployed during the manufacture of components having a small dimensionaltolerance.

The present inventors have also discovered that the thermoplasticcomposition may possess a relatively low melt viscosity, which allows itto readily flow into the mold cavity during production of the part. Forinstance, the composition may have a melt viscosity of about 20kilopoise or less, in some embodiments about 15 kilopoise or less, andin some embodiments, from about 0.1 to about 10 kilopoise, as determinedby a capillary rheometer at a temperature of 316° C. and shear rate of1200 seconds⁻¹. Among other things, these viscosity properties can allowthe composition to be readily injection molded into parts having verysmall dimensions without producing excessive amounts of flash.

Conventional shaping processes can be used for forming articles out ofthe thermoplastic composition including, without limitation, extrusion,injection molding, blow-molding, thermoforming, foaming, compressionmolding, hot-stamping, fiber spinning and so forth. Shaped articles thatmay be formed may include structural and non-structural shaped parts,for instance for automotive engineering thermoplastic assemblies as wellas industrial applications such a components of cooling tower pumps,water heaters, and the like. For instance thermoform sheets, foamedsubstrates, injection molded or blow molded components, fibers, and thelike can be formed from the thermoplastic composition.

According to one embodiment, the thermoplastic composition can beprocessed according to an injection molding method. The injectionmolding method includes the injection of the thermoplastic compositioninto a mold cavity where it is cooled until reaching the desiredejection temperature. As discussed above, the unique properties of theboron-containing nucleating agent of the thermoplastic composition canallow the cooling time and/or mold temperature of a molding cycle to besubstantially reduced. In addition to improving the properties of thecooling cycle, other aspects of the molding operation may also beenhanced. For example, as is known in the art, injection can occur intwo main phases—i.e., an injection phase and holding phase. During theinjection phase, the mold cavity is completely filled with the moltenthermoplastic composition. The holding phase is initiated aftercompletion of the injection phase in which the holding pressure iscontrolled to pack additional material into the cavity and compensatefor volumetric shrinkage that occurs during cooling. After the shot hasbuilt, it can then be cooled. In addition to reducing the cooling timeas discussed above, the improved properties of the thermoplasticcomposition may also allow for a lower holding time, which includes thetime required to pack additional material into the cavity and the timeat which this material is held at a certain pressure. Once cooling iscomplete, the molding cycle is completed when the mold opens and thepart is ejected, such as with the assistance of ejector pins within themold.

Any suitable injection molding equipment may generally be employed inthe present invention. Referring to FIG. 1, for example, one embodimentof an injection molding apparatus or tool 10 that may be employed in thepresent invention is shown. In this embodiment, the apparatus 10includes a first mold base 12 and a second mold base 14, which togetherdefine an article or component-defining mold cavity 16. The moldingapparatus 10 also includes a resin flow path that extends from an outerexterior surface 20 of the first mold half 12 through a sprue 22 to amold cavity 16. The resin flow path may also include a runner and agate, both of which are not shown for purposes of simplicity. Thethermoplastic composition may be supplied to the resin flow path using avariety of techniques. For example, the thermoplastic composition may besupplied (e.g., in the form of pellets) to a feed hopper attached to anextruder barrel that contains a rotating screw (not shown). As the screwrotates, the pellets are moved forward and undergo pressure andfriction, which generates heat to melt the pellets. Additional heat mayalso be supplied to the composition by a heating medium that iscommunication with the extruder barrel. One or more ejector pins 24 mayalso be employed that are slidably secured within the second mold half14 to define the mold cavity 16 in the closed position of the apparatus10. The ejector pins 24 operate in a well-known fashion to remove amolded part from the cavity 16 in the open position of the moldingapparatus 10.

A cooling mechanism may also be provided to solidify the resin withinthe mold cavity. In FIG. 1, for instance, the mold bases 12 and 14 eachinclude one or more cooling lines 18 through which a cooling mediumflows to impart the desired mold temperature to the surface of the moldbases for solidifying the molten material.

As a result of the boron-containing nucleating agent employed in thepresent invention, it has been discovered that the thermoplasticcomposition can be readily formed into parts having a wide range ofdifferent parts. The parts may be in the form of a substrate having anaverage thickness of about 25 millimeters or less, in some embodimentsfrom about 0.5 to about 15 millimeters, and in some embodiments, fromabout 1 millimeter to about 10 millimeters. Alternatively, the part maysimply possess certain features (e.g., walls, ridges, etc.) within theaverage thickness ranges noted above.

Regardless of the particular size, the present inventors have discoveredthat excellent mechanical properties can be achieved even whenrelatively short cooling times are employed. For instance, an injectionmolded part may exhibit a tensile strength of from about 100 to about500 MPa, in some embodiments from about 120 to about 400 MPa, and insome embodiments, from about 190 to about 350 MPa. The part may alsoexhibit a tensile break strain of about 0.5% or more, in someembodiments from about 0.6% to about 10%, and in some embodiments, fromabout 0.8% to about 3.5%; and/or a tensile modulus of from about 5,000MPa to about 25,000 MPa, in some embodiments from about 8,000 MPa toabout 22,000 MPa, and in some embodiments, from about 10,000 MPa toabout 20,000 MPa. The tensile properties may be determined in accordancewith ISO Test No. 527 (technically equivalent to ASTM D638) at 23° C.The parts may also exhibit a flexural strength of from about 20 to about500 MPa, in some embodiments from about 50 to about 400 MPa, and in someembodiments, from about 100 to about 350 MPa; a flexural break strain ofabout 0.5% or more, in some embodiments from about 0.6% to about 10%,and in some embodiments, from about 0.8% to about 3.5%; and/or aflexural modulus of from about 5,000 MPa to about 25,000 MPa, in someembodiments from about 8,000 MPa to about 22,000 MPa, and in someembodiments, from about 10,000 MPa to about 20,000 MPa. The flexuralproperties may be determined in accordance with ISO Test No. 178(technically equivalent to ASTM D790) at 23° C. The part may alsopossess a high impact strength, such as an Izod notched impact strengthgreater than about 4 kJ/m², in some embodiments from about 5 to about 40kJ/m², and in some embodiments, from about 6 to about 30 kJ/m², measuredat 23° C. according to ISO Test No. 180) (technically equivalent to ASTMD256, Method A).

The resulting molded parts may be employed in a wide variety ofdifferent components. One particular component that may incorporate anmolded part of the present invention is a liquid pump (e.g., waterpump). The liquid pump may be a direct lift pump, positive displacementpump (e.g., rotary, reciprocating, or linear), rotodynamic pump (e.g.,centrifugal), gravity pump, etc. Rotodynamic pumps, in which energy iscontinuously imparted to the pumped fluid by a rotating impeller,propeller, or rotor, are particularly suitable. In a centrifugal pump,for instance, fluid enters a pump impeller along or near to the rotatingaxis and is accelerated by the impeller, flowing radially outward into adiffuser or volute chamber, from which it exits into the downstreampiping. Such pumps are often used in automotive applications to move acoolant through the engine. Due to the high temperatures associated withautomotive engines, the thermoplastic composition is particularly wellsuited for use in the centrifugal pumps of such automotive coolingsystems. In certain embodiments, for example, all or a portion (e.g.,blades) of the water impeller may be formed from the thermoplasticcomposition. Centrifugal pumps also generally include a housing thatencloses certain components of the pump and protects them from heat,corrosion, etc. In some embodiments, some or all of the housing may beformed from the thermoplastic composition.

Referring to FIG. 2, one particular example of a centrifugal pump isshown that can employ the thermoplastic composition of the presentinvention. In the illustrated embodiment, the pump contains a rotaryshaft 201 supported on a housing 203 via a bearing 202. A pump impeller204, which may contain the thermoplastic composition, is rigidly fixedat an end of the rotary shaft 201. A pulley hub 205 is also rigidlyfixed on the base end portion of the rotary shaft 201. Between thebearing 202 and the pump impeller 204, a mechanical seal 206 is formedthat is constituted by a stationary member 206 a fixed on the side ofthe housing 203 and a rotary member 206 b fixedly engaged with therotary shaft 201. The pump may also include a housing 207, which cancontain the thermoplastic composition. The housing 207 may be affixed tothe pump housing 203 (e.g., with fastening bolts) so that a volutechamber 208 is defined therebetween. While not illustrated, a suctionportion and a discharge port may also be provided within the housing207.

Of course, the thermoplastic composition is not limited to the formationof water pumps or portions thereof, and it may be utilized in formingall manner of components, for instance components as may be incorporatedin a fluid handling system including pipes and sections of pipes,flanges, valves, valve seats, seals, sensor housings, thermostats,thermostat housings, diverters, linings, propellers, and so forth. Thecomposition may also employed in forming components that function in afluid environment, such as consumer products that encounter hightemperature fluids, e.g., heated beverage containers. Still further, thecomposition may be employed in completely different environments, suchas an electronic component. Examples of electronic components that mayemploy a molded part include, for instance, cellular telephones, laptopcomputers, small portable computers (e.g., ultraportable computers,netbook computers, and tablet computers), wrist-watch devices, pendantdevices, headphone and earpiece devices, media players with wirelesscommunications capabilities, handheld computers (also sometimes calledpersonal digital assistants), remote controllers, global positioningsystem (GPS) devices, handheld gaming devices, battery covers, speakers,camera modules, integrated circuits (e.g., SIM cards), etc.

Wireless electronic devices, however, are particularly suitable.Examples of suitable wireless electronic devices may include a desktopcomputer or other computer equipment, a portable electronic device, suchas a laptop computer or small portable computer of the type that issometimes referred to as “ultraportables.” In one suitable arrangement,the portable electronic device may be a handheld electronic device.Examples of portable and handheld electronic devices may includecellular telephones, media players with wireless communicationscapabilities, handheld computers (also sometimes called personal digitalassistants), remote controls, global positioning system (“GPS”) devices,and handheld gaming devices. The device may also be a hybrid device thatcombines the functionality of multiple conventional devices. Examples ofhybrid devices include a cellular telephone that includes media playerfunctionality, a gaming device that includes a wireless communicationscapability, a cellular telephone that includes game and email functions,and a handheld device that receives email, supports mobile telephonecalls, has music player functionality and supports web browsing.

Referring to FIGS. 3-4, one particular embodiment of an electronicdevice 100 is shown as a portable computer. The electronic device 100includes a display member 103, such as a liquid crystal diode (LCD)display, an organic light emitting diode (OLED) display, a plasmadisplay, or any other suitable display. In the illustrated embodiment,the device is in the form of a laptop computer and so the display member103 is rotatably coupled to a base member 106. It should be understood,however, that the base member 106 is optional and can be removed inother embodiments, such as when device is in the form of a tabletportable computer. Regardless, in the embodiment shown in FIGS. 3-4, thedisplay member 103 and the base member 106 each contain a housing 86 and88, respectively, for protecting and/or supporting one or morecomponents of the electronic device 100. The housing 86 may, forexample, support a display screen 120 and the base member 106 mayinclude cavities and interfaces for various user interface components(e.g., keyboard, mouse, and connections to other peripheral devices).Although the thermoplastic composition of the present invention maygenerally be employed to form any portion of the electronic device 100,for example for forming the cooling fan, it is typically employed toform all or a portion of the housing 86 and/or 88. When the device is atablet portable computer, for example, the housing 88 may be absent andthe thermoplastic composition may be used to form all or a portion ofthe housing 86. Regardless, due to the unique properties achieved by thepresent invention, the housing(s) or a feature of the housing(s) may bemolded to have a very small wall thickness, such as within the rangesnoted above.

Although not expressly shown, the device 100 may also contain circuitryas is known in the art, such as storage, processing circuitry, andinput-output components. Wireless transceiver circuitry in circuitry maybe used to transmit and receive radio-frequency (RF) signals.Communications paths such as coaxial communications paths and microstripcommunications paths may be used to convey radio-frequency signalsbetween transceiver circuitry and antenna structures. A communicationspath may be used to convey signals between the antenna structure andcircuitry. The communications path may be, for example, a coaxial cablethat is connected between an RF transceiver (sometimes called a radio)and a multiband antenna.

The present invention may be better understood with reference to thefollowing examples.

Test Methods

Melt Viscosity: The melt viscosity is determined as scanning shear rateviscosity and determined in accordance with ISO Test No. 11443(technically equivalent to ASTM D3835) at a shear rate of 1200 s⁻¹ andat a temperature of 316° C. using a Dynisco 7001 capillary rheometer.The rheometer orifice (die) had a diameter of 1 mm, a length of 20 mm,an UD ratio of 20.1, and an entrance angle of 180°. The diameter of thebarrel was 9.55 mm±0.005 mm and the length of the rod was 233.4 mm.

Recrystallization Temperature and Recrystallization Energy weredetermined by differential scanning calorimetry.

Example 1

A variety of boron nitride materials were utilized as nucleating agentsas follows:

BN-1—SP-2 grade boron nitride powder available from Denki Kagaku Kogyo.

BN-2—NX-1 grade boron nitride powder available from MomentivePerformance Materials, Inc.

BN-3—PCPS 3005 grade Combat® boron nitride powder available fromSaint-Gobain Ceramics.

BN-4—PT110 grade PolarTherm® boron nitride powder available fromMomentive Performance Materials, Inc.

BN-5—PT180 grade PolarTherm® boron nitride powder available fromMomentive Performance Materials, Inc.

BN-6—HCV grade boron nitride powder available from Momentive PerformanceMaterials, Inc.

BN-7—AC6111 grade boron nitride powder available from MomentivePerformance Materials, Inc.

The boron nitride materials had physical characteristics as reported bythe supplier provided in the table below:

Specific Average Graphi- surface Ratio of particle size tization area(SSA) particle Purity (μm) index (m²/g) size to SSA (%) BN-1 4 — — — 97BN-2 0.7 4 20 0.04 ~98.5 BN-3 0.9 — 20 0.45 ~98 BN-4 45 1 0.8 56 ~99.5BN-5 8 1.8 17 0.47 ~99.2 BN-6 9 >8 40 0.23 ~97 BN-7 1.2 >8 39 0.03 ~97.5

Thermoplastic compositions were formed including one of the boronnitride nucleating agents and additional components as described below:

Polyphenylene sulfide—Fortron® 0205 PPS

Glass fiber—10 μm diameter fiberglass 910a10c available from OCV™

Aminosilane—3-aminopropyltriethoxysilane—KBE-903 available fromShin-Etsu Silicone

Lubricant—Glycolube® P available from Lonza Group Ltd.

The components are mixed in a Werner Pfleiderer ZSK 25 co-rotatingintermeshing twin-screw extruder with a 25 mm diameter to form thesamples as described in the table below.

Glass PPS BN-1 BN-2 BN-3 BN-4 BN-5 BN-6 BN-7 Lubricant AminosilaneFibers Sample (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %)(wt. %) (wt. %) (wt. %) (wt. %) 1 59.3 — — — — — — — 0.3 0.4 40 2 59.25 0.05 — — — — — — 0.3 0.4 40 3 59.2 0.1 — — — — — — 0.3 0.4 40 4 59.10.2 — — — — — — 0.3 0.4 40 5 59.2 — 0.1 — — — — — 0.3 0.4 40 6 59.2 — —0.1 — — — — 0.3 0.4 40 7 59.2 — — — 0.1 — — — 0.3 0.4 40 8 59.2 — — — —0.1 — — 0.3 0.4 40 9 59.2 — — — — — 0.1 — 0.3 0.4 40 10 59.3 — — — — — —— 0.3 0.4 40 11 59.1 0.2 — — — — — — 0.3 0.4 40 12 59.1 — 0.2 — — — — —0.3 0.4 40 13 59.1 — — — — — 0.2 — 0.3 0.4 40 14 59.1 — — — — — — 0.20.3 0.4 40

Properties of pellets formed from the samples are determined, theresults of which are set forth in the table below.

Melt Re- Re- Viscosity Crystallization Crystallization Sample(kilopoise) Temp (° C.) Energy (kJ/g) 1 4.40 209.6 23.84 2 4.40 233.125.1 3 4.45 234.1 25.87 4 4.51 234.2 25.63 5 4.43 234 24.83 6 4.54 232.824.36 7 4.38 230.7 24.6 8 4.32 232.7 24.69 9 4.61 233.9 24.55 10 4.74224.2 23.71 11 4.91 233 25.16 12 4.42 232.4 23.95 13 4.62 233.8 24.42 144.77 234.8 25.23

As indicated above, the addition of the boron nitride nucleating agenthaving the smallest ratio of particle size to specific surface area(sample 14) has the higher recrystallization temperature, while controlsamples 1 and 10 and comparative sample 7 have much lowerrecrystallization temperatures.

These and other modifications and variations of the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

What is claimed is:
 1. A thermoplastic composition comprising aboron-containing nucleating agent and a polyarylene sulfide, theboron-containing nucleating agent having a graphitization index ofgreater than about 4, the nucleating agent having an average particlesize and a specific surface area, wherein the ratio of the averageparticle size to the specific surface area is between about 0.001 andabout 1 micrometers per square meter per gram, the thermoplasticcomposition having a recrystallization temperature of greater than about231° C. as determined according to differential scanning calorimetry. 2.The thermoplastic composition of claim 1, wherein the ratio of theaverage particle size to the specific surface area of theboron-containing nucleating agent is between about 0.01 and about 0.8.3. The thermoplastic composition of claim 1, wherein the averageparticle size of the boron-containing nucleating agent is less thanabout 10 micrometers.
 4. The thermoplastic composition of claim 1,wherein the specific surface area of the boron-containing nucleatingagent is greater than about 15 square meters per gram.
 5. Thethermoplastic composition of claim 1, wherein the graphitization indexof the boron-containing nucleating agent is greater than about
 5. 6. Thethermoplastic composition of claim 1, wherein the boron-containingnucleating agent is boron nitride.
 7. The thermoplastic composition ofclaim 1, wherein the boron-containing nucleating agent is in a hexagonalcrystalline form.
 8. The thermoplastic composition of claim 1, whereinthe polyarylene sulfide constitutes from about 30 wt. % to about 95 wt.% of the composition and the boron-containing nucleating agentconstitutes from about 0.01 wt. % to about 6 wt. % of the composition.9. The thermoplastic composition of claim 1, wherein the polyarylenesulfide is a polypropylene sulfide.
 10. The thermoplastic composition ofclaim 1, wherein the composition further comprises an impact modifier,mineral filler, fibrous filler, organosilane coupling agent, lubricant,disulfide, or a combination thereof.
 11. The thermoplastic compositionof claim 1, wherein the composition has a recrystallization energy ofgreater than about 24 kilojoules per gram as determined according todifferential scanning calorimetry.
 12. A molded part comprising thethermoplastic composition of claim
 1. 13. The molded part according toclaim 12, wherein the molded part is injection molded.
 14. A liquid pumpcomprising the molded part of claim
 12. 15. The liquid pump of claim 14,wherein the pump is a direct lift pump, positive displacement pump,rotodynamic pump, or gravity pump.
 16. The liquid pump of claim 14,wherein the pump is a centrifugal pump for circulating a coolant throughan automotive engine.
 17. An electronic component comprising the moldedpart of claim
 12. 18. The electronic component of claim 17, wherein thecomponent is a cellular telephone, laptop computer, small portablecomputer, wrist-watch device, pendant device, headphone or earpiecedevice, media player with wireless communication capabilities, handheldcomputer, remote controller, global positioning system device, handheldgaming device, battery cover, speaker, camera module, or integratedcircuit.
 19. A method for molding a thermoplastic composition, themethod comprising: shaping a thermoplastic composition, wherein thethermoplastic composition comprises a polyarylene sulfide and aboron-containing nucleating agent, the nucleating agent having agraphitization index of greater than about 4, the nucleating agenthaving an average particle size and a specific surface area, wherein theratio of the average particle size to the specific surface area isbetween about 0.001 and about 1, the thermoplastic composition having arecrystallization temperature of greater than about 231° C. asdetermined according to differential scanning calorimetry; subjectingthe thermoplastic composition to a cooling cycle.
 20. The method ofclaim 19, wherein the step of shaping the thermoplastic compositioncomprises injecting the thermoplastic composition into a mold cavity.21. The method of claim 20, wherein the mold temperature is from about50° C. to about 120° C.
 22. The method of claim 19, wherein a flashformed during the step of shaping the thermoplastic composition is about0.17 millimeters or less.
 23. The method of claim 19, the method furthercomprising combining the polyarylene sulfide with the boron-containingnucleating agent.
 24. The method of claim 19, wherein the total time ofthe cooling cycle is from about 1 to about 60 seconds.
 25. The method ofclaim 19, wherein the water is used as a cooling medium during thecooling cycle.